This invention relates to improvements in a dental handpiece, and more particularly to a transmission gear for a dental handpiece.
In the conventional transmission gear for a dental handpiece such as disclosed in the specification of the Japanese Patent Application Publication (not-examined) No. 129,492/1978, coupling members 16 and 17 are provided in both the axial and radial directions from a drive shaft 6, and these coupling members are not coupled to a driven shaft, but are selectively engageable with coupled members 18 or 19 of a driven sleeve 10.
It has been found, however, that it is not only difficult to make such a complicated device, but the selective engagement of these coupling members 16 and 17 with the coupled members 18 and 19 can not be carried out easily. In addition, the delivery of torque is carried out through the medium of these coupling and coupled members so that these members are worn out easily, resulting in inaccurate delivery of torque.
A principal object of this invention is to provide a transmission gear for a dental handpiece which includes a shiftable clutch shaft interposed between a drive shaft and a driven shaft, a collar bearing provided respectively at a middle portion and a planetary gear train at the rear end of the clutch, shaft whereby the torque of a driving motor can be properly delivered to the driven shaft.
Another object of this invention is to provide a transmission gear for a dental handpiece including an operating ring whereby a clutch shaft can be easily and rapidly shifted by a selective rotation of the operating ring to drive a dental tool at given speed.
Another object of this invention is to provide a transmission gear for a dental handpiece including no means of power delivery which will cause abrasion of the coupling and coupled members to ensure smooth rotation for a dental tool.
Still another object of this invention is to provide a dental handpiece which is comparatively simple and small, light in weight and at the same time desirably rigid, strong and durable.